[Dark Mode] Posts list: Re-set ghost style when switching filter tabs.

[ScoutHarris]

Fixes #13326

This fixes an issue where the ghost cells in the Blog Posts list would appear white instead of showing the ghost animation.

Note: there is a separate issue with the Search bar border color.

To test:

• Set the device to dark mode.
• On a slow network, go to Blog Posts.
• Switch between tabs.
• Verify the ghost cells animate.

Before	After

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[mindgraffiti]

✅ code
✅ UI tested